The beneficial aspects of calcium addition to steel have been well known for the purposes of inclusion modification. Various techniques have been used to introduce the calcium into the molten steel bath in a cost effective manner including the addition of bulk calcium and bulk alloy such as calcium silicon, the powder injection of calcium and various alloys and mixtures of calcium metals and the use of wires containing mixtures of calcium and other powders. However, because of the metallurgical properties of calcium, including a high vapor pressure, high buoyancy, low melting and boiling points, adding calcium to a molten steel bath presents a number of problems.
One method of treating molten ferrous material with calcium is continuously feeding steel clad solid calcium cored wires into the surface of the molten metal in steel-making ladles. This will be referred to herein as the surface feeding process. Currently, steel clad solid calcium cored wires are available in a stock of about 8-9 mm diameter calcium core wires and the quantity of calcium required for treating the molten ferrous metal in a steel-making ladles demand that the steel clad solid calcium wires be fed into the molten metal at a high velocity up to 400 feet per minute.
However, because of the high feeding velocity of the calcium cored wire, the release point of the calcium cored wire in the ladle with respect to the injection point is difficult to maintain and control. The release point being where the cored wire melts and becomes liquid bubbles of calcium within the molten ferrous metal.
The relationship between the injection point and the release point of the cored calcium wire can be better controlled if the feeding velocity of the solid calcium wire can be lowered. This can be achieved by increasing the quantity of calcium in the cored calcium wire per unit length. However, current technology for extruding solid calcium metal wire is limited to producing about 8-9 mm diameter stock wires and can not form larger diameter solid calcium wires.